dmaengine: dma-axi-dmac: Properly free struct axi_dmac_desc

dmaengine: dma-axi-dmac: Properly free struct axi_dmac_desc

Use axi_dmac_free_desc() to free fully the descriptor at fail path when
call axi_dmac_alloc_desc() in axi_dmac_prep_peripheral_dma_vec().

Fixes: 74609e568670 ("dmaengine: dma-axi-dmac: Implement device_prep_peripheral_dma_vec")
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260424-dma-dmac-handle-vunmap-v4-2-90f43412fdc0@analog.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>